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http://en.wikipedia.org/wiki/Gold
Gold is a dense, soft, shiny, malleable and ductile metal. It is a chemical element with the symbol Au and atomic number 79.Gold has a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water. Chemically, gold is a
transition metal and a
group 11 element. It is one of the least reactive chemical elements solid under standard conditions. The metal therefore occurs often in free elemental (native) form, as
nuggets or grains in rocks, in
veins and in
alluvial deposits. Less commonly, it occurs in minerals as gold compounds, usually with
tellurium.
Gold resists attacks by individual acids, but it can be dissolved by the
aqua regia (nitro-hydrochloric acid), so named because it dissolves gold. Gold also dissolves in alkaline solutions of
cyanide, which have been used in mining. Gold dissolves in
mercury, forming
amalgam alloys. Gold is insoluble in
nitric acid, which dissolves
silver and
base metals, a property that has long been used to confirm the presence of gold in items, giving rise to the term
the acid test.A total of 165,000
tonnes of gold have been mined in human history, as of 2009.
[2] This is roughly equivalent to 5.3 billion
troy ounces or, in terms of volume, about 8500 m
3, or a
cube 20.4 m on a side. The world consumption of new gold produced is about 50% in jewelry, 40% in investments, and 10% in industry.
[3]Besides its widespread monetary and symbolic functions, gold has many practical uses in
dentistry,
electronics, and other fields. Its high
malleability,
ductility, resistance to corrosion and most other chemical reactions, and conductivity of electricity led to many uses of gold, including
electric wiring, colored-glass production and even
gold leaf eating.
It has been claimed that most of the Earth's gold lies at its core, the metal's high density having made it sink there in the planet's youth. Virtually all of the gold that mankind has discovered is considered to have been deposited later by
meteorites which contained the element.
[4][5][6][7][8]